Solar thermal generates heat from sunlight, photovoltaics generates electricity – and both compete for the same roof space. For most single-family homes today, photovoltaics is the more versatile choice: its electricity can be used for everything, including heating via a heat pump, whereas solar thermal only provides heat. As a general rule, photovoltaics therefore belongs on the roof. (As of: July 2026)
Key points in brief
- The fundamental difference: Solar thermal produces heat (for hot water and heating), photovoltaics produces electricity.
- Both need the same sunlit roof area – side-by-side installations are rarely worthwhile on a typical single-family home roof.
- Photovoltaics is the all-rounder: the electricity heats via a heat pump, charges the car, runs the household – and what is left over brings feed-in remuneration.
- Solar thermal achieves high efficiencies for pure hot water generation, but is restricted to this one purpose.
- The combination of photovoltaics plus a heat pump has outstripped solar thermal in most new projects.
What is the difference between solar thermal and photovoltaics?
Both technologies sit on the roof, both use the sun – and yet they do fundamentally different things. Solar thermal captures the heat of the sunlight: a liquid circulates in the collectors, which heats up and transfers its heat to the hot water cylinder or the heating system. Photovoltaics, on the other hand, converts the light into electrical current – the technology guide explains how this works in detail.
The crucial point for your decision: heat can only be used as heat, electricity for almost anything – including to produce heat. This is exactly the reason why the two technologies no longer compete on an equal footing today.
Why is it an either/or question?
Because both need the same resource: a well-sunlit roof area. If you cover half of the south-facing roof with collectors, you can no longer cover it with modules – and vice versa. On a typical single-family home roof, space is limited enough that a side-by-side arrangement makes both systems too small to really fulfil their purpose.
There are exceptions – large roofs, special consumption profiles, existing systems – but the fundamental question remains: which technology extracts the greater benefit from your scarce space? And for most houses, this question has a clear answer.
The direct comparison
| Solar thermal | Photovoltaics | |
|---|---|---|
| Produces | Heat | Electricity |
| Use | Hot water, heating support | Household, heat pump, e-car, feed-in |
| Versatility | Restricted to heat | Universally applicable |
| Surplus | Difficult to use (heat can hardly be «fed in») | Remunerated or stored |
| Combination with a heat pump | Tends to compete | Complements ideally |
| Incentives | Possible cantonally | Federal one-off feed-in incentive + cantonal |
Simplified comparison, as of: July 2026. The planning for the specific property is decisive.
Two rows from this table usually decide the matter. The first is the surplus: if solar thermal produces more heat in summer than the house needs, it largely evaporates – hot water cannot be fed back into the grid. Photovoltaic surplus, on the other hand, brings feed-in remuneration or goes into the battery, car, and heat pump. The second is the heat pump: it has rearranged the distribution of roles on the roof.
What has the heat pump changed?
As long as houses were heated with oil or gas, solar thermal had its firm place: it was the direct way to turn sun into hot water. With the heat pump, a more elegant way has been added. The heat pump turns electricity into a multiple of heat – and photovoltaics provides this electricity. Instead of producing heat directly on the roof, you produce electricity and let the heat pump turn it into heat: more versatile, because the same electricity also runs everything else in the house.
That is why we see the combination of photovoltaics plus a heat pump almost consistently in new projects – and only rarely the classic thermal solar system. Where a functioning solar thermal system already exists, there is no reason to replace it; for new decisions, however, the choice today is clearly in favour of photovoltaics.
When can solar thermal still make sense?
For the sake of completeness, because sweeping judgements are rarely the whole truth: there are constellations in which heat generation on the roof retains its justification. A very high, year-round uniform hot water requirement – for example in certain multi-person households or businesses – can speak in favour of the high thermal efficiencies. The calculation also shifts where a heat pump is difficult for structural reasons.
For the typical single-family home in the region, however, the following applies: anyone planning a new roof today and wanting to use the area optimally will fare better with photovoltaics – ideally combined with a heat pump – in almost all cases. Solar thermal is not a bad technology; it has simply become the less versatile one for most houses.
The question «Shouldn't I rather use solar thermal for hot water?» almost always comes up in consultations from homeowners who have already looked into the topic a few years ago – back then, solar thermal was the obvious way. We rarely calculate with brochure figures then, but explain the logic: a square metre of roof, covered with modules, produces electricity that can also heat the water via the heat pump – and incidentally the fridge, the car, and the surplus for the grid. The same square metre with collectors can only do one thing: heat water, and in summer more of it than the house will ever need. At this point at the latest, the decision is usually made. We never advise expanding existing thermal systems, on the other hand – as long as they run, they do their job.
Frequently asked questions
Can I combine solar thermal and photovoltaics on the same roof?
Technically yes, practically rarely makes sense – both need the sunlit area, and divided, both end up too small. On large roofs or with special heating requirements, it can work out; on a typical single-family home roof, pure photovoltaic coverage is almost always the better use of the space.
Isn't solar thermal more efficient than photovoltaics?
When it comes to purely converting light into heat, solar thermal achieves higher efficiencies than photovoltaics when converting it into electricity – that is true. Only this comparison counts for little, because the heat is harder to use and can hardly be utilised as soon as there is more of it than needed. Versatility beats pure efficiency here.
What do I do with my existing solar thermal system?
Operate it as long as it runs – a replacement with photovoltaics is usually not worthwhile for a functioning system. If a roof renovation is due anyway or the thermal system reaches the end of its service life, the time has come to rethink the area.
Does photovoltaics also heat my house?
Not directly, but via the detour of electricity: in combination with a heat pump, the photovoltaics provide the electricity from which the heat pump produces heating warmth and hot water. This combination is the usual way today to heat with the sun – more versatile than direct heat generation via solar thermal.
Are there also incentives for solar thermal?
Yes, thermal solar systems are promoted in many cantons – unlike photovoltaics, however, they do not receive a federal one-off feed-in incentive. The decisive factor is the current regulations of your canton and your municipality.
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Sources: EnergieSchweiz (Basics of solar thermal and photovoltaics); Swissolar; empirical values from the planning practice of ecoEn GmbH, Zurich region.
Last updated: 9 July 2026 · Author: ecoEn editorial team
